Skip to main content

Full text of "The manufacture and properties of iron and steel"

See other formats


120                        METALLUBGY OF IRON AND STEEL,
calories. Assuming an iron with Si=0.5%, "Pól.5%, C=4.0%, and assuming that 4.0 per cent, of iron is burned to useful purpose,/the heat produced per 1000 kilos of iron will be as shown in Table VII-D, the total being about 50 per cent, more than in the acid converter.
TABLE VII-D. Production of Heat in the Basic Converter.
5 kg. silicon  ............................... 23,430 calories
35 kg. carbon............................... 40,700
40 kg. iron..................................  39,640
15 kg. phosphorus...........................57,315
Total ...'................................151,085
The pig-iron for basic-Bessemer work should contain less than 1.0 per cent, of silicon, a content of 0.5 to 0.6 per cent, being not unusual. It should carry from 1.0 to 2.0 per cent, of manganese to assist in removing sulphur. The phosphorus, according to Har-bord,* should be from 2.5 to 3.0 per cent., in order to have a margin of heat, but this assertion is probably based on English practice, as, in Germany, it is found that 2.0 per cent, of phosphorus is sufficient. The loss in the converter formerly ranged from 13 to 17 per cent, in different works, but now, in the best Westphalian plants, running on direct iron, it is as low as 10 per cent.
SEC. Vllg.óRecarburization.óRecarburization is the greatest problem of the basic-Bessemer process, for at the end of the operation the metal contains much more oxygen than an acid bath, while the slag, instead of being viscous and inactive, is liquid and has some loosely held oxide of iron. In making rail steel by the use of melted spiegel, this oxygen in metal and slag may give a reaction with the carbon of the recarburizer, and the carbonic oxide which is formed reduce some phosphorus from the slag. This, action is shown in Table VII-A, where the phosphorus was raised in the case of "pig-iron No. 1" from .087 before recarburization to .145 in the finished product, the latter figure being too high for good rail steel.                                          ,
When making soft steel by the addition of solid 'ferro-man-:
* Steel, p.,90.